Username is displayed too small on Registration confirmation page and proper punctuation should be added

Steps to reproduce

1. Logout
2. Click "Register" and fill the details of a new user: Username, including the First Name and Last Name (e.g. Username: U4, First Name: User, Last Name: Four)
3. Click "Register" button
4. On the registration confirmation page, observe the Welcome line

Expected results

All elements on the Welcome line are correctly proportioned and the punctuation is appropriate.

Actual results

The Username displayed between the round brackets is too small compared to the rest of the text (see screenshots).

However, if no First/Last Name are filled, only the username is displayed in this case, which is properly proportioned.

Also, after "Welcome" word, a comma and an exclamation sign should be added, like: "Welcome, User Four (U4)!"